First of all, the “Millers” isn’t a typo – apparently they didn’t do typos, at least in 1631 when the Second Quarto was published, so yeah, that’s how it was published.
So, did Shakespeare write this thing we’re about to embark on? The majority opinion is no. Edward Phillips says it was written by Robert Greene. Most other scholars say he’s completely full of it and his mama dresses him funny. Some modern scholars vote for Anthony Munday. Or maybe it was John Day. Sir Brian Vickers and Darren Freebury-Jones argue it was Thomas Kyd. As far as I can tell, no scholars at all have argued that the actual William By-Gosh Shakespeare wrote this thing.
So why are we doing it here? Well, it’s Charles the Second’s fault.
Once upon a time, folks found Em bound up with Mucedorus and The Merry Devil of Edmonton in a volume labeled “Shakespeare Vol. 1” in Chuckie Two’s library. Does anybody believe it’s Shakespeare? I wouldn’t say it’s a unanimous “no,” but it’s an enormous-majority-no. But what the heck, here we go.